A history of migraine is plausibly related to breast cancer risk, yet its association with breast cancer has never been reported in the literature. In women, the risk of migraine changes during menarche, menses, pregnancy, and menopause due to fluctuating estrogen levels. Particularly relevant to breast cancer risk, migraines in women are often associated with low estrogen states. Given that lifetime estrogen exposure is strongly related to breast cancer risk, we hypothesize that migraine sufferers may have a reduced risk of breast cancer. Additionally, evaluating the role of migraine medications is critical as some have been shown to be related to breast cancer risk. Most notably, non-steroidal anti-inflammatory drugs (NSAIDs) have been observed to modestly reduce breast cancer risk in several observational studies. We propose to investigate the associations between characteristics of migraine and medications used to prevent and treat migraine and risk of breast cancer using women enrolled in a recently completed population-based breast cancer case-control study. This study focused on identifying risk factors for ductal vs. lobular breast carcinomas, and we will attempt to conduct telephone interviews with the 514 invasive ductal cases, 530 invasive lobular cases, and 469 population-based controls enrolled in this study. In order to compare invasive ductal and invasive lobular carcinoma cases to controls, polytomous logistic regression will be used to calculate odds ratios (ORs) and 95% confidence intervals. We hypothesize that women with a history of migraine will have a reduced risk of breast cancer, and that women with early onset migraine, migraine associated with menses, frequent migraine, and more intense migraine will have particularly reduced risks. Further, we will explore the extent to which medications used to prevent or treat migraine may also reduce risk. The specific aims of the proposed pilot study are: (1) to investigate the relationships between characteristics of migraine, such as frequency, intensity, and timing, in women with a clinical diagnosis of migraine and women with migraine-like symptoms, and risk of invasive ductal and invasive lobular breast carcinomas;and (2) to investigate the relationship between over-the-counter and prescription medications used for migraine and risk of invasive ductal and invasive lobular breast carcinomas. This proposed work will provide insight into the role of migraine and migraine medication use in relation to breast cancer risk. The results of this study may enhance our understanding of factors that are associated with a reduced risk of breast cancer and ultimately may aid in identifying potentially new mechanisms relevant to breast cancer prevention. PUBLIC HEALTH RELEVANCE: We hypothesize that women with a history of migraine or women that use medications to prevent or treat migraines will have a reduced risk of breast cancer. Breast cancer is the most commonly diagnosed cancer among women in the United States and is the 2nd leading cause of cancer mortality;therefore, identifying new risk factors for breast cancer is of considerable public health importance.